Modern smartphone apps are resurrecting the spyware trend that plagued the web ten years ago, but today's users are often unable to do anything to block their demographic data from being used to enhance the advertisements they see.

A report by the Wall Street Journal, part of a series examining privacy issues in computing and in particular the web, examined 101 popular smartphone apps for both iOS and Android devices to find what data they were sharing with advertisers.

The study found that more than half (56) sent the devices' unique serial number to advertisers for tracking purposes, while 47 made some use of users' location data. Five of the apps sent users' "age, gender or other personal details" to outside sources.

In some cases, this data is purposely entered by the user for reasons related to the apps' functionality, and some apps do outline that this data is also used for advertising purposes.

The Journal did not specify how it selected the apps that it tested or whether the roughly 50 apps on each platform represented a comparable selection, but it did note that "among the apps tested, the iPhone apps transmitted more data than the apps on phones using Google Inc.'s Android operating system."

The report also pointed out that not all apps were available for Android, including the company's own news app. "Because of the test's size," the report stated, "it's not known if the pattern holds among the hundreds of thousands of apps available." Apple lists over 300,000 apps for iOS devices, while Android's catalog of apps, ringtones and wallpapers is greater than 100,000 titles.

Mobile adware here to stay, hard to avoid

The findings might be news to some smartphone users, who are rarely presented with simple, straightforward information about individual apps' privacy policy. However, the use of unique device identifiers, location and demographic data to "enhance ad results" are have become core foundations of the mobile ad industry.

The report cited Michael Becker of the Mobile Marketing Association as saying, "in the world of mobile, there is no anonymity," and noting that the mobile phone is "always with us. It's always on."

The significant revenues tied to advertising are also pushing some vendors to relax individuals' privacy protections in order to maximize profits, a situation reflecting the history of adware on desktop PCs.

A history of adware

Adware began infecting PCs in the mid 90s, particularly as the web helped connect users to networks in a way that also made them easy to reach with ads. Platform vendors readily embraced the new avenues for revenues adware presented, with Netscape inventing web browser "cookies" as a way for web site owners to track visitors, while Microsoft's Windows 98 turned the PC desktop into an overt billboard for advertisers.